Alloy steel antifriction bearing element



July 27, 1943. F, WRIGHT ET AL 2,325,088

ed Nov. 4, 1939 s @mnk SWUJM M George. [9. hwrssen nnnnnn rs ttornego Patent e d July 27, 1943 ALLOY STEEL ANTIFBIOTION BEARING ELEMENT Frank L. Wright, Stamford, Conn, and George V. Luerssen, Muhlenberg Park, Pa., assignors of one-half to The Carpenter Steel Company, Reading, Pa., a corporation of New Jersey, and one-half to Norma-Hoffmann Bearings Corporation, Stamford, Conn., a corporation of New York Application November 4, 1939, Serial No. 302,824

1 Claim. (Cl. 75-126) This invention relates to improvedalloy steel antifriction bearing elements orthe like which require heat-treatment in processing for the securing of metallurgical properties required for special service, and more particularly to alloysteel anti-friction bearings which are normally subjected to the inherently destructive action of anti-friction rollers'or balls riding upon them under pressure of relatively heavy and rapidly rotated loads. The improved method of hardening such products which is incidentally presented being separately set forth and claimed in a required continuing divisional application, Serial No."372,126, filed December 28, 1940.

The fact that special metallurgical properties are peculiarly called for in such products because of the character and incident strains and wear and tear of such service, is well known, and alloy steels having contents of the known elements carbon, chromium, manganese and silicon have been heretofore proposed; but we have found that the problem of fully and satisfactorily protual effects of these alloying elements when such products are subjected to hardening heat-treatof uniform wearing quality in the bearing surment, and to -called-for control ofsuch treatment.

Our invention involves particularly the discovery that use of the known hardening element manganese in needed percentages, incidentally causes the production of hurtful non-metallic inclusions.

and that this bar to its adequate use is satisfactorily removed by combining with it an at least neutralizing high content of silicon. Also that this provision for employing such needed content 'of manganese and silicon in connection with the known hardening element chromium, enables a determined slow-hardening treatment as by aircooling preliminary to required full hardening by oil-quenching, so as to secure the uniform hardening throughout all sections which is called for ance of hurtfulinternal stresses in reduced crosssectional portions, as a and b, incident to needed faces.

The essential quality called for in anti-friction bearings particularly, is the complete hardening throughout which calls for ability of the alloy steel employed to harden uniformly in all required to satisfactorily attain these requisite properties we have recognized the fact that the usual hardening element chromium cannot be satisfactorily relied upon in such products because such steels must be hardened in water with resulting limited penetration and liability of. cracks, hurtful distortion and size change.

We have found by systematic experimentation 1 that addition of the known alloying element manganese for the purpose of making the product -oil hardening as desired, is practically limited because of a resulting detrimental amount of non-metallics apparently due to itsamnity for lining constituents; and have further discovered the vital facts that this limitation of the use of manganese is avoidable, and required oil-hardening quality satisfactorily secured, by adding in connection with the relatively large amount of oil-hardening manganese required for this purpose, a correspondingly large content of the element silicon whereby such. natural productionof harmful non-metallics by the needed manganese is corrected and desired oil-hardening fitting to the rollers cor balls d, and the securing quality secured.

The extensivescientiflc experimenting which has resulted in highly satisfactory manufacture of our improved alloy steel and products made therefrom, shows that our improved alloy essentially comprises an ordinary content of .80% to 1.20% of carbon, and is characterized by a total content of the alloying elements manganese, sili-- con and chromium amounting to between 5% and 10% with the manganese between 1% and 3% and correspondingly high silicon content over 1.50% and not exceeding 3.00%a practically preferred specific formula being substantially as follows: Carbon .85%, chromium 1.75%, manganese 1.75% and silicon 2.00%, the rest being subs an y all iron without character-affecting impurities and the sum of chromium, man ganes'eand silicon being not less than 5%. It will be here noted, that specific formula embodies the rule that the sum of manganese and silicon exceeds the chromium content, and the silicon exceeds the manganese content; the sum of chromium, manganese and silicon being more than 5%, with a .85% carbon content, and with the rest being substantially all iron.

Alloy steels made to the formula standardized by the Society of AutomotiveEngineers as Number 52,100 are used by some ball and roller bearing manufacturers for antifriction bearings and requires drastic water quenching of the heavy sections. The formula of this steel has percentages as follows: Carbon .95-1.10, manganese .20-50, silicon less than .30, chromium 1.20-1.50. Other alloy steels provided for such products fall within the following percentage limits. Carbon .85-1.20. Manganese .803.0. Silicon .50-1.50. Chromium .902-.50. These may be fully quenched in oil in intermediate ring sections, but require the somewhat hazardous and less desirable water quench when large sections are heat treated to produce the desired full hardness. It will also be noted that in each of these cases, the silicon is relatively low compared to the manganese, and in the Number 52,100, the manganese is relatively low, compared to the chromium. In 52,100, the chromium, manganese and silicon is less than 5%, and in the other formula the minimum of chromium, manganese and silicon, is less than 5% and not more than Our improved steel alloy permits the preliminary use of a less drastic quench than a direct quench in oil; and furthermore, permits the largest ring sections now encountered in bearing pracr c re by using the oil hardening treatment. The less drastic quench referred to as preceding the oil quench, is most simply and satisfactorily effected by air-cooling the alloy from a heating temperature range of approximately 1500 F. to 1650 as commonly practiced in the art in connection with oil hardening steels, for a time interval determined by the size and sections of the part, followed immediately by quenching in oil, as is known, at a temperature of above approximately 1200 F., depending on the size of the section. The delayed air-oil quench as applied to the formulated alloy permits-the useof a single alloy for a wide variety of sections, from onehalf inch thick light-wall hearings to heavy walled bearings having a section thickness up to five inches or larger, without developing hurtful quenching stresses or cracks as when more drastic quenching practices are used. Dimension changes and distortion resulting from quenching are maintained within desirable close tolerance limits through the use of the formulated analysis and the proper delayed air-oil quench. The high silicon and chromium reduce the scale formin tendencies of parts during treatment, and when the optimum best conditions. for heating are used,

, tice to be fully hardened throughout the desired structural condition best suited for long life under destructive stresses.

We have found that a specially high range of from over 5% to 10% of total content of the alloying elements manganese, silicon and chromium best enable the preliminary air-cooling before final oil quenching which we have determined is needed for avoidance of distortions in size-and form particularly where the ring crosssection is substantially varied from the heavier main portion; this high content permitting a definitely lengthened air exposure before the oilquenching, whereby final .uniform hardening throughout is secured with practical freedom from distortion.

We have found that the critical range of content in our improved steel alloy is substantially: Carbon .80 to 1.20%, chromium 1.50 to 4.00%, manganese 1.00 to 3%, silicon over 1.50% to 3.00%, the rest being substantially all iron as stated, and the chromium, manganese, and silicon amounting to substantially 5% with a practical maximum of 10%; the specific contents thereof, and air-hardening and oil quenching processing being adaptable to the proportions of the heat-treated products, within the scope of our invention as defined in the subjoined claim. In distinction to the known art, the manganese and silicon contents is higher than the chromium content, and the silicon content is substantially equal to or higher than the manganese content. The high manganese content assures the oil quench possibility, in contrast to the water quench where the chromium is dominant, and the still higher silicon content prevents the high manganese content from forming harmful nonmetallic inclusions.

What we claim is:

An alloy steel antifriction bearing element free from harmful internal stresses and free from harmful non-metallic inclusions from linings used in the process of manufacture of the alloy, comprising 1.50 to 4% chromium, 1 to 3% manganese, 1.50 to 3% silicon, .80 to 1.20% carbon, and the balance substantially all iron, the content of chromium, manganese 'and silicon exceeding 5% but not 10%, the content of manganese and silicon together exceeding the chromium, the manganese content suflicient for deep hardening by oil quenching, the content of silicon at least equal to the manganese, and the content of chromium sufficient for a wide allowable quenching range.

' FRANK L. WRIGHT.

GEORGE V. LUERSSEN. 

